6.2.1 Controlling user agent

Controlling user agentsMUST implement the following partial interface:

partial interfacePresentation {    attributePresentationRequest?defaultRequest;};

ThedefaultRequest attributeMUST return thedefault presentation request if any,null otherwise. On setting, thedefault presentation requestMUST be set to the new value.

Thecontrolling user agentSHOULD initiate presentation using thedefault presentation request only when the user has expressed an intention to do so via a user gesture, for example by clicking a button in the browser chrome.

To initiate presentation using thedefault presentation request, thecontrolling user agentMUST follow the steps tostart a presentation from a default presentation request.

Support for initiating a presentation using thedefault presentation request isOPTIONAL.

6.2.2 Receiving user agent

Receiving user agentsMUST implement the following partial interface:

partial interfacePresentation {    readonly attributePresentationReceiver?receiver;};

Thereceiver attributeMUST return thePresentationReceiver instance associated with thereceiving browsing context and created by thereceiving user agent when thereceiving browsing context iscreated. In any otherbrowsing context (includingnested browsing contexts of thereceiving browsing context) itMUST returnnull.

6.3.1 Constructing aPresentationRequest

When thePresentationRequest constructor is called, thecontrolling user agentMUST run these steps:

Input

url orurls, thepresentation request URLs

Output

APresentationRequest object

1. If the document object'sactive sandboxing flag set has thesandboxed presentation browsing context flag set, then throw aSecurityError and abort these steps.
2. Ifurls is an empty sequence, thenthrow aNotSupportedError and abort all remaining steps.
3. If a singleurl was provided, leturls be a one item array containingurl.
4. LetpresentationUrls be an empty list of URLs.
5. For each URLU inurls:
   1. ResolveU relative to the API base URL specified by thecurrent settings object, and add the resulting absolute URL (if any) topresentationUrls.
   2. If the resolve a URL algorithm failed, thenthrow aSyntaxError exception and abort all remaining steps.
6. If any member ofpresentationUrls is not ana priori authenticated URL, then throw aSecurityError and abort these steps.
7. Construct a newPresentationRequest object withpresentationUrls as itspresentation request URLs and return it.

6.3.2 Selecting a presentation display

When thestart method is called, theuser agentMUST run the following steps toselect a presentation display.

Input

presentationRequest, thePresentationRequest object that received the call tostart

Output

APromise

1. If the algorithm isn'tallowed to show a popup, return aPromise rejected with anInvalidAccessError exception and abort these steps.
2. LettopContext be thetop-level browsing context of thecontrolling browsing context.
3. If there is already an unsettledPromise from a previous call tostart intopContext or anybrowsing context in thelist of descendant browsing contexts oftopContext, return a newPromise rejected with anOperationError exception and abort all remaining steps.
4. LetP be a newPromise.
5. ReturnP, but continue running these stepsin parallel.
6. If theuser agent is notmonitoring the list of available presentation displays, run the steps tomonitor the list of available presentation displaysin parallel.
7. LetpresentationUrls be thepresentation request URLs ofpresentationRequest.
8. Request user permission for the use of apresentation display and selection of one presentation display.
9. If either of the following is true:
   1. Thelist of available presentation displays is empty and will remain so before the request for user permission is completed.
   2. No member in thelist of available presentation displays is anavailable presentation display for any member ofpresentationUrls.
   Then run the following steps:
   1. RejectP with aNotFoundError exception.
   2. Abort all remaining steps.
10. If the userdenies permission to use a display, rejectP with anNotAllowedError exception, and abort all remaining steps.
11. Otherwise, the usergrants permission to use a display; letD be that display.
12. Run the steps tostart a presentation connection withpresentationRequest,D, andP.

6.3.3 Starting a presentation from a default presentation request

When the user expresses an intent to start presentation of a document on a presentation display using the browser chrome (via a dedicated button, user gesture, or other signal), that user agentMUST run the following steps tostart a presentation from a default presentation request. If nodefault presentation request is set on the document, these stepsMUST not be run.

Input

W, the document on which the user has expressed an intent to start presentation

presentationRequest, the non-null value ofnavigator.presentation.defaultRequest set onW

D, thepresentation display that is the target for presentation

1. LetpresentationUrls be thepresentation request URLs ofpresentationRequest.
2. If there is nopresentation request URL forpresentationRequest for whichD is anavailable presentation display, then abort these steps.
3. Run the steps tostart a presentation connection withpresentationRequest andD.

6.3.4 Starting a presentation connection

When theuser agent is tostart a presentation connection, itMUST run the following steps:

Input

presentationRequest, thePresentationRequest that is used to start the presentation connection

D, the selectedpresentation display

P, an optionalPromise that will be resolved with a newpresentation connection

1. LetI be a newvalid presentation identifier unique among allpresentation identifiers for knownpresentation connections in theset of controlled presentations. To avoid fingerprinting, implementationsSHOULD set thepresentation identifier to aUUID generated by following forms 4.4 or 4.5 of [rfc4122].
2. Create a newPresentationConnectionS.
3. Set thepresentation identifier ofS to I.
4. LetpresentationUrls be thepresentation request URLs ofpresentationRequest.
5. Set thepresentation URL forS to the firstpresentationUrl inpresentationUrls for which there exists an entry(presentationUrl, D) in thelist of available presentation displays.
6. Set thepresentation connection state ofS toconnecting.
7. AddS to theset of controlled presentations.
8. IfP is provided,resolveP withS.
9. Queue a task tofire atrusted event with the nameconnectionavailable, that uses thePresentationConnectionAvailableEvent interface, with theconnection attribute initialized toS, atpresentationRequest. The event must not bubble, must not be cancelable, and has no default action.
10. LetU be the user agent connected to D.
11. If the next step fails, abort all remaining steps andclose the presentation connectionS witherror ascloseReason, and a human readable message describing the failure ascloseMessage.
12. Using an implementation specific mechanism, tellU tocreate a receiving browsing context withD,presentationUrl, andI as parameters.
13. Establish a presentation connection withS.

6.3.5 Reconnecting to a presentation

When thereconnect method is called, theuser agentMUST run the following steps toreconnect to a presentation:

Input

presentationRequest, thePresentationRequest object thatreconnect was called on

presentationId, a validpresentation identifier

Output

P, aPromise

1. LetP be a newPromise.
2. ReturnP, but continue running these steps in parallel.
3. Search theset of controlled presentations for aPresentationConnection that meets the following criteria:
   • Itscontrolling browsing context is the current browsing context
   • Itspresentation connection state is notterminated
   • Itspresentation URL is equal to one of thepresentation request URLs ofpresentationRequest
   • Itspresentation identifier is equal topresentationId
4. If such aPresentationConnection exists, run the following steps:
   1. LetexistingConnection be thatPresentationConnection.
   2. ResolveP withexistingConnection.
   3. If thepresentation connection state ofexistingConnection isconnecting orconnected, then abort all remaining steps.
   4. Set thepresentation connection state ofexistingConnection toconnecting.
   5. Establish a presentation connection withexistingConnection.
   6. Abort all remaining steps.
5. Search theset of controlled presentations for the firstPresentationConnection that meets the following criteria:
   • Itscontrolling browsing context is not the currentbrowsing context
   • Itspresentation connection state is notterminated
   • Itspresentation URL is equal to one of thepresentation request URLs ofpresentationRequest
   • Itspresentation identifier is equal topresentationId
6. If such aPresentationConnection exists, run the following steps:
   1. LetexistingConnection be thatPresentationConnection.
   2. Create a newPresentationConnectionnewConnection.
   3. Set thepresentation identifier ofnewConnection topresentationId.
   4. Set thepresentation URL ofnewConnection to thepresentation URL ofexistingConnection.
   5. Set thepresentation connection state ofnewConnection toconnecting.
   6. AddnewConnection to theset of controlled presentations.
   7. ResolveP withnewConnection.
   8. Queue a task tofire atrusted event with the nameconnectionavailable, that uses thePresentationConnectionAvailableEvent interface, with theconnection attribute initialized tonewConnection, atpresentationRequest. The event must not bubble, must not be cancelable, and has no default action.
   9. Establish a presentation connection withnewConnection.
   10. Abort all remaining steps.
7. RejectP with aNotFoundError exception.

6.3.6 Event Handlers

The following are the event handlers (and their corresponding event handler event types) that must be supported, as event handler IDL attributes, by objects implementing thePresentationRequest interface:

6.4.1 The set of presentation availability objects

Theuser agentMUST keep track of theset of presentation availability objects created by thegetAvailability method. Theset of presentation availability objects is represented as a set of tuples(A,availabilityUrls), initially empty, where:

1. A is a livePresentationAvailability object.
2. availabilityUrls is the list ofpresentation request URLs for thePresentationRequest whengetAvailability was called on it to createA.

6.4.2 The list of available presentation displays

Theuser agentMUST keep alist of available presentation displays. Thelist of available presentation displays is represented by a list of tuples(availabilityUrl, display). An entry in this list means thatdisplay is currently anavailable presentation display foravailabilityUrl. This list ofpresentation displays may be used for starting new presentations, and is populated based on an implementation specific discovery mechanism. It is set to the most recent result of the algorithm tomonitor the list of available presentation displays.

While theset of presentation availability objects is not empty, theuser agentMAYmonitor the list of available presentation displays continuously, so that pages can use thevalue property of aPresentationAvailability object to offer presentation only when there are available displays. However, theuser agent may not support continuous availability monitoring in the background; for example, because of platform or power consumption restrictions. In this case thePromise returned bygetAvailability isrejected, and the algorithm tomonitor the list of available presentation displays will only run as part of theselect a presentation display algorithm.

When theset of presentation availability objects is empty (that is, there are noavailabilityUrls being monitored), user agentsSHOULD NOTmonitor the list of available presentation displays to satisfy the power saving non-functional requirement. To further save power, theuser agentMAY also keep track of whether a page holding aPresentationAvailability object is in the foreground. Using this information, implementation specific discovery ofpresentation displays can be resumed or suspended.

6.4.3 Getting thepresentation displays availability information

When thegetAvailability method is called, the user agentMUST run the following steps:

Input

presentationRequest, thePresentationRequest object that received the call togetAvailability

Output

APromise

1. If there is an unsettledPromise from a previous call togetAvailability on presentationRequest, return thatPromise and abort these steps.
2. Otherwise, letP be a newPromise constructed in theJavaScript realm ofpresentationRequest.
3. ReturnP, but continue running these stepsin parallel.
4. If the user agent is unable to continuouslymonitor the list of available presentation displays in the background, but can later find presentation displays in order to start a connection, then:
   1. RejectP with aNotSupportedError exception.
   2. Abort all the remaining steps.
5. If thepresentation display availability forpresentationRequest is notnull, then:
   1. ResolveP with the request'spresentation display availability.
   2. Abort all the remaining steps.
6. Set thepresentation display availability forpresentationRequest to a newly createdPresentationAvailability object constructed in theJavaScript realm ofpresentationRequest, and letA be that object.
7. Create a tuple(A,presentationUrls) and add it to theset of presentation availability objects.
8. Run the algorithm tomonitor the list of available presentation displays.
   Note

   The monitoring algorithm must be run at least one more time after the previous step to pick up the tuple that was added to theset of presentation availability objects.
9. ResolveP withA.

6.4.4 Monitoring the list of available presentation displays

If theset of presentation availability objects is non-empty, or there is a pending request toselect a presentation display, theuser agentMUSTmonitor the list of available presentation displays by running the following steps:

1. LetavailabilitySet be a shallow copy of theset of presentation availability objects.
2. If there is a pending request toselect a presentation display for aPresentationRequest and if thePresentationRequest'spresentation display availability isnull, then run the following substeps:
   1. LetA be a newly createdPresentationAvailability object.
   2. Create a tuple(A,presentationUrls) wherepresentationUrls is thePresentationRequest'spresentation request URLs and add it toavailabilitySet.
3. LetnewDisplays be an empty list.
4. If theuser agent is unable to retrievepresentation displays (e.g., because the user has disabled this capability), then skip the following step.
5. Retrievepresentation displays (using an implementation specific mechanism) and setnewDisplays to this list.
6. Set thelist of available presentation displays to the empty list.
7. For each member(A,availabilityUrls) ofavailabilitySet, run the following steps:
   1. SetpreviousAvailability to the value ofA'svalue property.
   2. LetnewAvailability befalse.
   3. For eachavailabilityUrl inavailabilityUrls, run the following step:
      1. For eachdisplay innewDisplays, ifdisplay is anavailable presentation display foravailabilityUrl, then run the following steps:
         1. Insert a tuple(availabilityUrl, display) into thelist of available presentation displays, if no identical tuple already exists.
         2. SetnewAvailability totrue.
   4. IfA'svalue property has not yet been initialized, then setA'svalue property tonewAvailability and skip the following step.
   5. IfpreviousAvailability is not equal tonewAvailability, thenqueue a task to run the following steps:
      1. SetA'svalue property tonewAvailability.
      2. Fire a simple event namedchange atA.

When apresentation display availability object is eligible for garbage collection, theuser agentSHOULD run the following steps:

1. LetA be the newly deceasedPresentationAvailability object
2. Find and remove any entry(A,availabilityUrl) in theset of presentation availability objects.
3. If theset of presentation availability objects is now empty and there is no pending request toselect a presentation display, cancel any pending task tomonitor the list of available presentation displays for power saving purposes, and set thelist of available presentation displays to the empty list.

6.4.5 InterfacePresentationConnectionAvailableEvent

[Constructor(DOMStringtype,PresentationConnectionAvailableEventIniteventInitDict),SecureContext,Exposed=Window]interfacePresentationConnectionAvailableEvent :Event {    [SameObject]    readonly attributePresentationConnectionconnection;};dictionaryPresentationConnectionAvailableEventInit :EventInit {    requiredPresentationConnectionconnection;};

Acontrolling user agentfires atrusted event namedconnectionavailable on aPresentationRequest when a connection associated with the object is created. It is fired at thePresentationRequest instance, using thePresentationConnectionAvailableEvent interface, with theconnection attribute set to thePresentationConnection object that was created. The event is fired for each connection that is created for thecontroller, either by thecontroller callingstart orreconnect, or by thecontrolling user agent creating a connection on the controller's behalf viadefaultRequest.

Areceiving user agentfires atrusted event namedconnectionavailable on aPresentationReceiver when an incoming connection is created. It is fired at thepresentation controllers monitor, using thePresentationConnectionAvailableEvent interface, with theconnection attribute set to thePresentationConnection object that was created. The event is fired for all connections that are created whenmonitoring incoming presentation connections.

Theconnection attributeMUST return the value it was set to when thePresentationConnection object was created.

When thePresentationConnectionAvailableEvent constructor is called, theuser agentMUST construct a newPresentationConnectionAvailableEvent object with itsconnection attribute set to theconnection member of thePresentationConnectionAvailableEventInit object passed to the constructor.

6.5.1 Establishing a presentation connection

When theuser agent is toestablish a presentation connection using apresentation connection, itMUST run the following steps:

Input

presentationConnection, thePresentationConnection object that is to be connected

1. If thepresentation connection state ofpresentationConnection is notconnecting, then abort all remaining steps.
2. Request connection ofpresentationConnection to thereceiving browsing context. Thepresentation identifier ofpresentationConnectionMUST be sent with this request.
3. If connection completes successfully,queue a task to run the following steps:
   1. Set thepresentation connection state ofpresentationConnection toconnected.
   2. Fire a simple event namedconnect atpresentationConnection.
4. If the connection cannot be completed,close the presentation connectionS witherror ascloseReason, and a human readable message describing the failure ascloseMessage.

6.5.2 Sending a message throughPresentationConnection

Letpresentation message data be the payload data to be transmitted between two browsing contexts. Letpresentation message type be the type of that data, one oftext orbinary.

When theuser agent is tosend a message through apresentation connection, itMUST run the following steps:

Input

presentationConnection, thepresentation connection connected to the other browsing context

messageOrData, thepresentation message data to send to the other browsing context

1. If thestate property ofpresentationConnection is notconnected,throw an InvalidStateError exception.
2. If theclosing procedure ofpresentationConnection has started, then abort these steps.
3. Letpresentation message typemessageType bebinary ifmessageOrData is of typeArrayBuffer,ArrayBufferView, orBlob. LetmessageType betext ifmessageOrData is of typeDOMString.
4. Using an implementation specific mechanism, transmit the contents ofmessageOrData as thepresentation message data andmessageType as thepresentation message type to thedestination browsing context.
5. If the previous step encounters an unrecoverable error, then abruptlyclose the presentation connectionpresentationConnection witherror ascloseReason, and acloseMessage describing the error encountered.

6.5.3 Receiving a message throughPresentationConnection

When theuser agent has received a transmission from the remote side consisting ofpresentation message data andpresentation message type, itMUST run the following steps toreceive a message through aPresentationConnection:

Input

presentationConnection, thepresentation connection receiving the message

messageType, thepresentation message type of the message

messageData, thepresentation message data of the message

1. If thestate property ofpresentationConnection is notconnected, abort these steps.
2. Letevent be a newly createdtrusted event that uses theMessageEvent interface, with the event typemessage, which does not bubble, is not cancelable, and has no default action.
3. Initialize theevent's data attribute as follows:
   1. IfmessageType istext, then initializeevent'sdata attribute tomessageData with typeDOMString.
   2. IfmessageType isbinary, andbinaryType attribute is set to "blob", then initializeevent'sdata attribute to a newBlob object withmessageData as its raw data.
   3. IfmessageType isbinary, andbinaryType attribute is set to "arraybuffer", then initializeevent'sdata attribute to a newArrayBuffer object whose contents aremessageData.
4. Queue a task tofireevent atpresentationConnection.

If theuser agent encounters an unrecoverable error whilereceiving a message throughpresentationConnection, itMUST abruptlyclose the presentation connectionpresentationConnection witherror ascloseReason. ItSHOULD use a human readable description of the error encountered ascloseMessage.

6.5.4 InterfacePresentationConnectionCloseEvent

enumPresentationConnectionCloseReason {"error","closed","wentaway"};[Constructor(DOMStringtype,PresentationConnectionCloseEventIniteventInitDict),SecureContext,Exposed=Window]interfacePresentationConnectionCloseEvent :Event {    readonly attributePresentationConnectionCloseReasonreason;    readonly attributeDOMStringmessage;};dictionaryPresentationConnectionCloseEventInit :EventInit {    requiredPresentationConnectionCloseReasonreason;DOMStringmessage ="";};

APresentationConnectionCloseEvent is fired when apresentation connection enters aclosed state. Thereason attribute provides the reason why the connection was closed. It can take one of the values ofPresentationConnectionCloseReason:

• error means that the mechanism for connecting or communicating with a presentation entered an unrecoverable error.
• closed means that either thecontrolling browsing context or thereceiving browsing context that were connected by thePresentationConnection calledclose.
• wentaway means that the browser closed the connection, for example, because the browsing context that owned the connection navigated or was discarded.

When thereason attribute iserror, the user agentSHOULD set themessage attribute to a human readable description of how the communication channel encountered an error.

When thePresentationConnectionCloseEvent constructor is called, theuser agentMUST construct a newPresentationConnectionCloseEvent object, with itsreason attribute set to thereason member of thePresentationConnectionCloseEventInit object passed to the constructor, and itsmessage attribute set to themessage member of thisPresentationConnectionCloseEventInit object if set, to an empty string otherwise.

6.5.5 Closing aPresentationConnection

When theuser agent is tostart closing a presentation connection, itMUST do the following:

Input

presentationConnection, thepresentation connection to be closed

closeReason, thePresentationConnectionCloseReason describing why the connection is to be closed

closeMessage, a human-readable message with details of why the connection was closed

1. If thepresentation connection state ofpresentationConnection is notconnecting orconnected then abort the remaining steps.
2. Set thepresentation connection state ofpresentationConnection toclosed.
3. Start to signal to thedestination browsing context the intention to close the correspondingPresentationConnection, passing thecloseReason to that context. The user agent does not need to wait for acknowledgement that the correspondingPresentationConnection was actually closed before proceeding to the next step.
4. IfcloseReason is notwentaway, then locally run the steps toclose the presentation connection withpresentationConnection,closeReason, andcloseMessage.

When theuser agent is toclose a presentation connection, itMUST do the following:

Input

presentationConnection, thepresentation connection to be closed

closeReason, thePresentationConnectionCloseReason describing why the connection is to be closed

closeMessage, a human-readable message with details of why the connection was closed.

1. If there is a pendingclose the presentation connection task forpresentationConnection, or aclose the presentation connection task has already run forpresentationConnection, then abort the remaining steps.
2. Queue a task to run the following steps:
   1. If thepresentation connection state ofpresentationConnection is notconnecting,connected, orclosed, then abort the remaining steps.
   2. If thepresentation connection state ofpresentationConnection is notclosed, set it toclosed.
   3. If thepresentationConnection was created as a result ofmonitoring incoming presentation connections in areceiving browsing context, run the following sub-steps.
      1. RemovepresentationConnection from theset of presentation controllers.
      2. Populate thepresentation controllers monitor with theset of presentation controllers.
   4. Fire atrusted event with the nameclose, that uses thePresentationConnectionCloseEvent interface, with thereason attribute initialized tocloseReason and themessage attribute initialized tocloseMessage, atpresentationConnection. The event must not bubble, must not be cancelable, and has no default action.

6.5.6 Terminating a presentation in a controlling browsing context

When acontrolling user agent is toterminate a presentation in a controlling browsing context usingconnection, itMUST run the following steps:

1. If thepresentation connection state ofconnection is notconnected orconnecting, then abort these steps.
2. Otherwise, for eachknown connection in theset of controlled presentations in thecontrolling user agent:
   1. If thepresentation identifier ofknown connection andconnection are equal, and thepresentation connection state ofknown connection isconnected orconnecting, thenqueue a task to run the following steps:
      1. Set thepresentation connection state ofknown connection toterminated.
      2. Fire a simple event namedterminate atknown connection.
3. Send a termination request for the presentation to itsreceiving user agent using an implementation specific mechanism.

6.5.7 Terminating a presentation in a receiving browsing context

When any of the following occur, thereceiving user agentMUSTterminate a presentation in a receiving browsing context:

1. Thereceiving user agent is tounload a document corresponding to thereceiving browsing context, e.g. in response to a request tonavigate that context to a new resource.
2. The user requests to terminate the presentation via thereceiving user agent.
   Note

   This could happen by an explicit user action, or as a policy of the user agent. For example, thereceiving user agent could be configured to terminate presentations whosePresentationConnection objects are all closed for 30 minutes.

3. Acontrolling user agentsends a termination request to thereceiving user agent for that presentation.

When areceiving user agent is toterminate a presentation in a receiving browsing context, itMUST run the following steps:

1. LetP be the presentation to be terminated, letallControllers be theset of presentation controllers that were created forP, andconnectedControllers an empty list.
2. For eachconnection inallControllers, run the following steps:
   1. If thepresentation connection state ofconnection isconnected, then addconnection toconnectedControllers.
   2. Set thepresentation connection state ofconnection toterminated.
3. If there is areceiving browsing context forP, and it has a document forP that is not unloaded,unload a document corresponding to thatbrowsing context, remove thatbrowsing context from the user interface anddiscard it.
4. For eachconnection inconnectedControllers,queue a task to send a termination confirmation forP using an implementation specific mechanism to thecontrolling user agent that owns thedestination browsing context forconnection.
   Note

   Only one termination confirmation needs to be sent percontrolling user agent.

6.5.8 Handling a termination confirmation in a controlling user agent

When areceiving user agent is tosend a termination confirmation for a presentationP, and that confirmation was received by acontrolling user agent, thecontrolling user agentMUST run the following steps:

1. For eachconnection in theset of controlled presentations that was connected toP,queue a task to run the following steps:
   1. If thepresentation connection state ofconnection is notconnected orconnecting, then abort the following steps.
   2. Set thepresentation connection state ofconnection toterminated.
   3. Fire a simple event namedterminate atconnection.

6.5.9 Event Handlers

The following are the event handlers (and their corresponding event handler event types) that must be supported, as event handler IDL attributes, by objects implementing thePresentationConnection interface:

6.6.1 Creating a receiving browsing context

When theuser agent is tocreate a receiving browsing context, itMUST run the following steps:

Input

D, apresentation display chosen by the user

presentationUrl, thepresentation request URL

presentationId, thepresentation identifier

1. Create a newtop-level browsing contextC, set to display content onD.
2. Set thesession history ofC to be the empty list.
3. Set thesandboxed modals flag and thesandboxed auxiliary navigation browsing context flag onC.
4. If thereceiving user agent implements [PERMISSIONS], set thepermission state of allpermission descriptor types forC to"denied".
5. Create a new emptycookie store forC.
6. Create a new empty store forC to holdHTTP authentication states.
7. Create a new emptyapplication cache storage forC.
8. If thereceiving user agent implements [INDEXEDDB], create a new empty storage for IndexedDBdatabases for C.
9. If thereceiving user agent implements [WEBSTORAGE], create a new empty storage forsession storage areas and local storage areas forC.
10. If thereceiving user agent implements [SERVICE-WORKERS], create a new emptylist of registered service worker registrations and a new emptycaches forC.
11. NavigateC topresentationUrl.
12. Startmonitoring incoming presentation connections forC withpresentationId andpresentationUrl.

Allnested browsing contextscreated by the presented document, i.e. that have thereceiving browsing context as theirtop-level browsing context,MUST also have restrictions 2-4 above. In addition, theyMUST have thesandboxed top-level navigation browsing context flag set. All of thesebrowsing contextsMUST also share the same browsing state (storage) for features 5-10 listed above.

Thetop-level browsing contextMUST NOT be allowed to navigate itself, except bynavigating to a fragment identifier. This allows the user to grant permission based on the presentation URL shown whenselecting a presentation display.

Window clients andworker clients associated with thereceiving browsing context and itslist of descendant browsing contexts must not be exposed toservice workers associated with each other.

When thereceiving browsing context is terminated, anyservice workers associated with it and thebrowsing contexts in itslist of descendant browsing contextsMUST be unregistered and terminated. Any browsing state associated with thereceiving browsing context and thebrowsing contexts in itslist of descendant browsing contexts, includingsession history, thecookie store, anyHTTP authentication state, theapplication cache, anydatabases, thesession storage areas, thelocal storage areas, thelist of registered service worker registrations and thecachesMUST be discarded and not used for any otherbrowsing context.

Thereceiving user agentSHOULD fetch resources in areceiving browsing context with an HTTPAccept-Language header that reflects the language preferences of thecontrolling user agent (i.e., with the sameAccept-Language that the controlling user agent would have sent). This will help thereceiving user agent render the presentation with fonts and locale-specific attributes that reflect the user's preferences.

6.7.1 Monitoring incoming presentation connections

When thereceiving user agent is to startmonitoring incoming presentation connections in areceiving browsing context fromcontrolling browsing contexts, itMUST listen to and accept incoming connection requests from acontrolling browsing context using an implementation specific mechanism. When a new connection request is received from acontrolling browsing context, thereceiving user agentMUST run the following steps:

Input

I, thepresentation identifier passed by thecontrolling browsing context with the incoming connection request

presentationId, thepresentation identifier used tocreate the receiving browsing context

presentationUrl, thepresentation request URL used tocreate the receiving browsing context

1. IfpresentationId andI are not equal, refuse the connection and abort all remaining steps.
2. Create a newPresentationConnectionS.
3. Set thepresentation identifier ofS to I.
4. Set thepresentation URL ofS topresentationUrl.
5. Establish the connection between the controlling andreceiving browsing contexts using an implementation specific mechanism.
6. If connection establishment completes successfully, set the presentation connection state ofS toconnected. Otherwise, set thepresentation connection state ofS toclosed and abort all remaining steps.
7. AddS to theset of presentation controllers.
8. If thepresentation controllers monitor isnull, run the following stepsin parallel.
   1. Let thepresentation controllers monitor be a newPresentationConnectionList constructed in theJavaScript realm of thePresentationReceiver object of thereceiving browsing context.
   2. Populate thepresentation controllers monitor with theset of presentation controllers.
   3. If thepresentation controllers promise is notnull,resolve thepresentation controllers promise with thepresentation controllers monitor.
   4. Abort all remaining steps.
9. Otherwise, run the following stepsin parallel.
   1. Populate thepresentation controllers monitor with theset of presentation controllers.
   2. Queue a task tofire atrusted event with the nameconnectionavailable, that uses thePresentationConnectionAvailableEvent interface, with theconnection attribute initialized toS, at thepresentation controllers monitor. The event must not bubble, must not be cancelable, and has no default action.

6.7.2 Event Handlers

The following are the event handlers (and their corresponding event handler event types) that must be supported, as event handler IDL attributes, by objects implementing thePresentationConnectionList interface: